I did exactly what you are asking about. As stated above, the breaker must be upgraded.
For mounting I started with the non windlass Grady hatch configuration. Then I mounted the Profish 700 on the flat hatch.
I wanted a straight line from the windlass to anchor resulting in the windlass slightly covering the opening hatch. That was easily reminded with a little sanding of the lid (the overlap is very minor).
I used the existing electrical wiring.
The boat is a Marlin 300.